Aliphatic polyester resin composition and films containing the same

ABSTRACT

The invention provides an aliphatic polyester resin composition that contains 100 parts by weight of an aliphatic polyester resin and from 10 to 60 parts by weight of at least one compound of a formula (1):  
                 
 
     wherein n indicates an integer of from 1 to 9, R 1  to R 4  each independently represent an alkyl group having from 1 to 17 carbon atoms, and when n is 2 or more, R 3  may differ in different units, a film formed of the composition, and packages with the film. The aliphatic polyester film of the invention keeps the degradability in the natural environment that is intrinsic to lactic acid-based polymer, and has good heat resistance, flexibility, transparency and adhesiveness, and, in addition, the plasticizer does not migrate on the surface of the film. Accordingly, the film is favorably used in a broad range for various industrial materials, for example, for films for wrapping or packaging foods, electronic appliances, medicines, chemicals, cosmetics, etc., for films for agricultural use, for films for civil engineering and construction use, for adhesive tapes, etc.

TECHNICAL FIELD

[0001] The present invention relates to an aliphatic polyester resincomposition, a film that comprises the resin composition, and packageswith the film. Precisely, the invention relates to an aliphaticpolyester resin composition which is degradable in the naturalenvironment and contains a specific plasticizer; to an aliphaticpolyester film which comprises the resin composition and has good heatresistance, transparency, flexibility and adhesiveness and from whichthe plasticizer does not migrate to its surface; and to packages withthe aliphatic polyester film.

BACKGROUND ART

[0002] The problem with plastic wastes is highlighted these days.Plastic wastes such as wrapping materials are, after used by users,discarded and incinerated, or disposed of for land reclamation, etc.However, when such plastic wastes are incinerated, the heat ofcombustion is high and there occurs a problem in point of the curabilityof incineration furnaces. Polyvinyl chloride and the like give harmfulgas and cause a pollution problem. Further, when they are disposed offor land reclamation, the shaped plastics do not degrade andsemi-permanently remain as refuse that has the original shape, and theirinfluence on the natural environment is problematic. Given thatsituation, various biodegradable plastics that are completely consumedby microorganisms in the natural environment to degrade into naturalside products of carbon dioxide and water have been invented and havenow amounted to the level of practical use.

[0003] For such biodegradable plastics, known is a composition ofpolylactic acid or thermoplastic polymer that comprises, as theessential ingredients, lactic acid and any other hydroxycarboxylic acid.For example, it is known that they have high mechanical strength and canbe worked into containers and films of practical durability. However,the polymer has a high modulus of elasticity and has high toughness, butits flexibility is low. Therefore, it is unsuitable to applications ofsoft film of polyethylene, polypropylene, polyvinyl chloride, etc.

[0004] For softening resin, generally known is a method of addingplasticizer to it. Studies of using various types of plasticizer forsoftening resin have heretofore been made. For example, JP-A2000-302956(EP1029890A) describes an aliphatic polyester composition that comprisesan aliphatic polyester and, as a plasticizer, at least one compoundselected from compounds (A) of the following formula:

[0005] wherein at least one of R₁, R₂ and R₃ is an acyl group havingfrom 6 to 18 carbon atoms, and the remainder is a hydrogen atom or anacetyl group,

[0006] and compounds (B) of a reaction product of a condensate of from 2to 10 molecules of glycerin with a carboxylic acid having from 6 to 18carbon atoms.

[0007] This says that specific examples of the compounds (A) includeglycerin diacetomonocaprylate, glycerin diacetomonolaurate and glycerindiacetomonooleate, and the compounds (B) are obtained through reactionof one mol of a glycerin condensate with from 0.8 to 1.2 mols of acarboxylic acid having from 6 to 18 carbon atoms, and their specificexamples include tetraglycerin monocaprylate, decaglycerin monolaurateand decaglycerin oleate.

[0008] This further says that the aliphatic polyester film obtained fromthe composition has excellent heat resistance and flexibility and noplasticizer migration of the film.

[0009] The film that comprises the compounds serving as plasticizer hasexcellent heat resistance and flexibility and no plasticizer migrationof the film, but a film having high adhesion force to objects such asglass containers wrapped with it is desired.

DISCLOSURE OF THE INVENTION

[0010] Accordingly, the subject matter of the invention is to provide analiphatic polyester resin composition which is degradable in the naturalenvironment and contains a specific plasticizer; an aliphatic polyesterfilm which comprises the resin composition and has good heat resistance,transparency, flexibility and adhesiveness and from which theplasticizer does not migrate to its surface; and packages with thealiphatic polyester film.

[0011] We, the present inventors have assiduously studied to solve theproblems noted above, and, as a result, have found that, in an aliphaticpolyester film formed of a resin composition that contains an aliphaticpolyester resin and, as a plasticizer, a compound of a formula (1):

[0012] wherein n indicates an integer of from 1 to 9, R₁ to R₄ eachindependently represent an alkyl group having from 1 to 17 carbon atoms,and when n is 2 or more, R₃ may differ in different units, theplasticizer does not migrate, and the film has good transparency, heatresistance, flexibility and adhesiveness. On the basis of thesefindings, we have reached the present invention.

[0013] Specifically, the invention is characterized by the following [1]to [10]:

[0014] [1] An aliphatic polyester resin composition comprising 100 partsby weight of an aliphatic polyester resin and from 10 to 60 parts byweight of at least one compound of a formula (1):

[0015] wherein n indicates an integer of from 1 to 9, R₁ to R₄ eachindependently represent an alkyl group having from 1 to 17 carbon atoms,and when n is 2 or more, R₃ may differ in different units.

[0016] [2] An aliphatic polyester film having at least one layer of afilm of the aliphatic polyester resin composition according to above[1].

[0017] [3] The aliphatic polyester film according to above [2], of whicha storage modulus (E′) at 20° C. is from 1×10⁷ to 2×10⁹ Pa, and a losstangent (tan δ) indicating the ratio of a loss Young's modulus (E″) tothe storage modulus (E′), (E″/E′) is from 0.1 to 1.0.

[0018] [4] The aliphatic polyester film according to above [2] or [3],wherein the aliphatic polyester resin is at least one polyester selectedfrom polylactic acid, and a copolymer of lactic acid with any otheraliphatic hydroxycarboxylic acid.

[0019] [5] The aliphatic polyester film according to any one of [2] to[4], of which the haze is from 0.05 to 3% when its thickness is 10 μm.

[0020] [6] The aliphatic polyester film according to any one of [2] to[4], of which the heat-resistant temperature falls between 100 and 170°C.

[0021] [7] The aliphatic polyester film according to any one of [2] to[4], of which the degree of crystallinity is from 10 to 60%.

[0022] [8] The aliphatic polyester film according to any one of [2] to[4], of which the thickness is from 5 to 1000 μm.

[0023] [9] The aliphatic polyester film according to any one of [2] to[4], which is for wrapping or packaging.

[0024] [10] A package of an object wrapped or packaged with thealiphatic polyester film according to any one of [2] to [4].

[0025] In the invention, the storage modulus (E′), and the loss tangent(tan δ) that indicates the ratio of loss Young's modulus (E″) to storagemodulus (E′), (E″/E′) are meant to indicate the values measuredaccording to the method mentioned below.

[0026] Using a dynamic solid viscoelastometer (Rheometric's ModelRSAII), a film sample having a length of 40 mm (MD direction), a widthof 5 mm (TD direction) and a mean thickness of from 5 to 15 μm ismeasured at a temperature falling between −100 and 230° C., at a heatingrate of 5° C./min and at a frequency of 1 Hz. The storage modulus (E′)at 20° C. of the sample is read, and the value tan δ that indicates theratio of the loss Young s modulus (E″) to the storage modulus (E′),(E″/E′) is calculated.

BEST MODES OF CARRYING OUT THE INVENTION

[0027] The invention is described in detail hereinunder.

[0028] The aliphatic polyester resin composition of the invention isproduced by adding, as a plasticizer, at least one compound of formula(1) described above to an aliphatic polyester resin followed by mixingthem.

[0029] The aliphatic polyester resin for use in the invention containsat least 40 mol %, preferably at least 50 mol %, more preferably atleast 60 mol % of lactic acid units in the molecule. Concretely, itincludes (1) polylactic acid, and copolymer of lactic acid with anyother aliphatic hydroxycarboxylic acid, (2) aliphatic polyesterscomprising polyfunctional polysaccharides and lactic acid units, (3)aliphatic polyesters comprising aliphatic polyvalent carboxylic acidunits, aliphatic polyvalent alcohol units and lactic acid units, and (4)their mixtures. These are hereinafter referred to as lactic acid-basedpolymer, a generic term for them. Of those, preferred are polylacticacid and copolymer of lactic acid with any other aliphatichydroxycarboxylic acid in view of the transparency and thehydrolyzability of the films to be obtained from them.

[0030] Lactic acid includes L-lactic acid and D-lactic acid. Unlessotherwise specifically indicated, lactic acid simply referred to in theinvention indicates both L-lactic acid and D-lactic acid. Also unlessotherwise specifically indicated, the molecular weight of polymerindicates a weight-average molecular weight thereof. The polylactic acidfor use in the invention includes poly(L-lactic acid) of which theconstitutive units are of L-lactic acid alone, poly(D-lactic acid) ofwhich the constitutive units are of D-lactic acid alone, andpoly(DL-lactic acid) that comprises L-lactic acid units and D-lacticacid units in a varying ratio. In the copolymer of lactic acid with anyother aliphatic hydroxycarboxylic acid, the other aliphatichydroxycarboxylic acid includes glycolic acid, 3-hydroxybutyric acid,4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid,6-hydroxycaproic acid, etc.

[0031] For producing the polylactic acid for use in the invention,employable is any of a method of direct dehydrating condensation ofL-lactic acid, D-lactic acid, or DL-lactic acid, or a method of ringopening polymerization of a cyclic dimer, lactide, of any of theselactic acids. The ring opening polymerization may be carried out in thepresence of a hydroxyl group-having compound of higher alcohols,hydroxycarboxylic acids, etc. For producing the copolymer of lactic acidwith any other aliphatic hydroxycarboxylic acid, employable is any of amethod of dehydrating polycondensation of any of the above-mentionedlactic acids with any of the above-mentioned aliphatic hydroxycarboxylicacids, or a method of ring opening copolymerization of a cyclic dimer,lactide, of any of the above-mentioned lactic acids with a cyclicderivative of the above-mentioned hydroxycarboxylic acids.

[0032] The polyfunctional polysaccharides to be used for producing thealiphatic polyesters comprising polyfunctional polysaccharides andlactic acid units include, for example, cellulose, cellulosenitrate,methyl cellulose, ethyl cellulose, celluloid, viscose rayon, regeneratedcellulose, cellophane, cupra, copperammoniarayon, cuprophane, Bemberg,hemicellulose, starch, achropectin, dextrin, dextran, glycogen, pectin,chitin, chitosan, arabic gum, guar gum, locust bean gum, acacia gum, andtheir mixtures and their derivatives. Of those, especially preferred arecellulose acetate and ethyl cellulose.

[0033] For producing the aliphatic polyester resin that containspolyfunctional polysaccharides and lactic acid units, employable is anyof a method of reacting the above-mentioned polyfunctionalpolysaccharides with the above-mentioned polylactic acid or copolymer oflactic acid with any other aliphatic hydroxycarboxylic acid, or a methodof reacting the above-mentioned polyfunctional polysaccharides with anyof the above-mentioned lactic acids, cyclic esters, etc.

[0034] The aliphatic polycarboxylic acid to be used for producing thealiphatic polyesters comprising aliphatic polyvalent carboxylic acidunits, aliphatic polyalcohol units and lactic acid units includes, forexample, oxalic acid, succinic acid, malonic acid, glutaric acid, adipicacid, pimelic acid, suberic acid, azelaicacid, undecane-diacid,dodecane-diacid, and their anhydrides. Their mixtures may also be used.The aliphatic polyvalent alcohol includes, for example, ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol, dipropyleneglycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol,1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, tetramethylene glycol,1,4-cyclohexanedimethanol, etc.

[0035] For producing the aliphatic polyesters comprising aliphaticpolyvalent carboxylic acid units, aliphatic polyvalent alcohol units andlactic acid units, employable is any of a method of reacting theabove-mentioned aliphatic polyvalent carboxylic acid and theabove-mentioned aliphatic polyvalent alcohol with the above-mentionedpolylactic acid or copolymer of lactic acid with any other aliphatichydroxycarboxylic acid, or a method of reacting the above-mentionedaliphatic polyvalent carboxylic acid and the above-mentioned aliphaticpolyalcohol with any of the above-mentioned lactic acids, cyclic esters,etc.

[0036] The molecular weight of the aliphatic polyester resin in theinvention has some influence on the workability, the strength and thedegradability of the films to be formed of the resin. Resin having a lowmolecular weight forms films of low strength, and the films will bebroken when put under tension while in use. In addition, the filmsrapidly degrade. On the contrary, resin having a high molecular weightis poorly workable and it is difficult to form the resin into films.Taking these points into consideration, the molecular weight of thealiphatic polyester resin for use in the invention preferably fallsbetween about 10,000 and about 1,000,000, more preferably between about100,000 and about 300,000.

[0037] In the invention, at least one compound of formula (1) is used asthe plasticizer for the aliphatic polyester resin. The compounds offormula (1) are obtained by acylating (esterifying) all the hydroxylgroups in a glycerin condensate with an acylating agent in an ordinarymanner, for which the amount of the acylating agent to be used is overthe amount that corresponds to the number of the hydroxyl groups. Thusobtained according to the method, the hydroxyl value of the acylatedproduct of the glycerin condensate is at most 20, preferably at most 5.The glycerin condensate to be used in producing the compounds of formula(1) is a condensate of from 2 to 10 molecules of glycerin, includingdiglycerin, triglycerin, tetraglycerin, decaglycerin, etc. The acylatingagent includes acetic anhydride, carboxylic acid chlorides having from 1to 18 carbon atoms, etc.

[0038] The value n in formula (1) has some influence on thecompatibility of the compounds with resin and on the flexibility of thefilms to be formed of the resin composition. If n is too large, thecompatibility of the compounds with resin is not good, and, in addition,the modulus of elasticity of the films formed increases and theflexibility of the films lowers. The number of carbon atoms toconstitute the alkyl group for R₁ to R₄ has some influence on theflexibility of the films formed. If the number of carbon atoms toconstitute the alkyl group is too large, the modulus of elasticity ofthe films formed increases and the flexibility of the films lowers. Fromthese viewpoints, n in formula (1) is an integer of from 1 to 9,preferably from 1 to 5. R₁ to R₄ each are an alkyl group having from 1to 17 carbon atoms, preferably from 1 to 5 carbon atoms. In case where nand R₁ to R₄ each fall within the range, the compounds of formula (1)are well compatible with the aliphatic polyester resin for use in theinvention and give a uniform resin composition, and the films formed ofthe composition are highly flexible.

[0039] R₁ to R₄ may be the same alkyl group or may be different alkylgroups. In addition, R₃ may differ in different glycerin units.Concretely, the compounds are tetraacetyldiglycerin,tetraoctanoyldiglycerin, pentastearoyltriglycerin, etc.

[0040] The amount of the plasticizer to be in the resin composition hassome influence on the degree of crystallinity, the flexibility, the heatresistance and the adhesiveness of the films formed of the resincomposition. If the amount of the plasticizer therein is too large, thedegree of crystallinity and the heat resistance of the films lower; butif too small, the films could not be well flexible. From theseviewpoints, the amount of the plasticizer, compound of formula (1) to bein the resin composition is from 10 to 60 parts by weight, preferablyfrom 15 to 50 parts by weight relative to 100 parts by weight of thealiphatic polyester resin therein. When the amount of the plasticizerfalls within the range, the films formed of the resin composition have asuitable degree of crystallinity and have good flexibility and heatresistance, and, in addition, their self-adhesiveness and adhesivenessto objects to be wrapped with them are both good.

[0041] Not detracting from its properties, the resin composition of theinvention may contain any other plasticizer. For example, a compoundobtained through reaction of one mol of a condensate of from 2 to 10molecules of glycerin with from 0.8 to 1.2 mols of an aliphaticcarboxylic acid having from 6 to 18 carbon atoms may be added to andmixed with the resin composition. Concretely, the compound includestetraglycerin monocaprylate, tetraglycerin monostearate, tetraglycerinmonooleate, hexaglycerin monolaurate, hexaglycerin monooleate,decaglycerin monopropionate, decaglycerin monolaurate, decaglycerinmonobehenate, decaglycerin monostearate, decaglycerin monooleate, etc.Typical commercial products of the compounds are Riken Vitamin's tradename, Poem J-0381 (decaglycerin monooleate, hydroxyl value 529), itstrade name, Poem J-0021 (decaglycerinmonolaurate, hydroxyl value 615),its trade name, Poem J-4581 (tetraglycerin monooleate, hydroxyl value250), etc. The amount of the additional plasticizer that may be in theresin composition is at most 20 parts by weight relative to 100 parts byweight of the compound of formula (1) therein.

[0042] Not interfering with the object of the invention, any otheradditives than the compounds of formula (1) may also be added to thealiphatic polyester resin composition of the invention, depending on theuse of the composition. The additives include antiblocking agents suchas silica, calcium carbonate, titania, mica, talc; lubricants, forexample, hydrocarbons such as liquid paraffin, polyethylene wax,aliphatic acids such as stearic acid, hydroxy-fatty acids, fatty acidamides, alkylenebis-fatty acid amides, lower alcohol esters of fattyacids, polyvalent alcohol esters of fatty acids, polyglycol esters offatty acids, aliphatic alcohols, polyvalent alcohols, polyglycols, metalsoap such as calcium stearate; antistatic agents such as salts of fattyacids, sulfate esters of higher alcohols, salts of sulfate esters ofliquid fatty oils, sulfate salts of aliphatic amines and aliphaticamides, salts of phosphate esters of aliphatic alcohols, sulfonate saltsof dibasic fatty acid esters, sulfonate salts of aliphatic amides, alkylallyl sulfonate salts, aliphatic amine salts, quaternary ammonium salts,alkylpyridinium salts, polyoxyethylene alkyl ethers, polyoxyethylenealkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters,polyoxyethylene sorbitan alkyl esters, imidazoline derivatives, higheralkylamines; antifoggants, for example, glycerin fatty acid esters suchas glycerin monostearate, sorbitan fatty acid esters such as sorbitanmonolaurate, sorbitan monooleate, as well as polyglycerin fatty acidesters, propylene glycol fatty acid esters; UV absorbents, for example,benzotriazoles such as 2-(2′-hydroxy-5′-methylphenyl)benzotriazole,benzophenones such as 2-hydroxy-4-methoxybenzophenone, salicylic acidderivatives such as p-tert-butylphenyl salicylate; thermal stabilizers,for example, phenolic compounds such as paramethoxyphenol, phosphitecompounds such as triphenyl phosphite, sulfur-containing compounds suchas 2-mercaptobenzimidazole, amine compounds such as phenylnaphthylamine;antioxidants; discoloration inhibitors; fillers and pigments such asbarium sulfate, titanium oxide, kaolin, carbon black; and flameretardants, for example, halogen compounds such as decabromodiphenylether, antimony compounds such as antimony trioxide.

[0043] For adding the plasticizer of formula (1) to aliphatic polyesterresin and mixing them in the invention, employable is a method ofuniformly mixing the aliphatic polyester resin, the plasticizer andoptionally any other additives by the use of a high-speed or low-speedstirrer or the like, followed by melt-kneading the resulting mixture ina high-performance single-screw or multi-screw extruder, etc. Ingeneral, the resin composition of the invention is preferably in theform of pellets, rods, powder, etc.

[0044] Next, the aliphatic polyester film of the invention and oneexample of a method for producing it are described below.

[0045] The resin composition of the invention is melt-extruded into afilm, through an extruder equipped with a T-die. Preferably, thethus-obtained film is stretched with rolls in the flow direction(machine direction—hereinafter referred to as MD direction), and thenstretched with a tenter in the transverse direction (in the directionperpendicular to the machine direction—hereinafter referred to as TDdirection). The order of the stretching operations may be opposite tothe above. After thus stretched, the film is then heat-set under tensionto be an oriented polyester film. For mono-axial orientation, the filmmay be stretched in any of MD or TD direction.

[0046] The melt-extrusion temperature for the aliphatic polyester resincomposition that contains various additives as above preferably fallsbetween 100 and 280° C., more preferably between 130 and 250° C. If themolding temperature is too low, the molding stability will be poor andthe films being molded will be under overload. Contrary to this, if themolding temperature is too high, the aliphatic polyester may decomposeand it is unfavorable since the molecular weight of the polyesterlowers, the strength of the films may lower and the films may discolor.

[0047] Preferably, the aliphatic polyester film of the invention is atleast uniaxially stretched by 1.5 to 5 times in any of MD or TDdirection. More preferably, it is biaxially stretched in both MD and TDdirections, and it is a biaxially-oriented film. In producing suchoriented films, if the draw ratio is smaller than 1.5 times, the degreeof crystallinity could not increase in the oriented films and the filmscould not enjoy the stability with time of mechanical properties anddimensional accuracy. On the other hand, if the draw ratio is largerthan 5 times, it is unfavorable since the films will lose theflexibility and will be broken while stretched. Preferably, thestretching temperature falls between the glass transition temperature(Tg) of the aliphatic polyester resin to form the films and (Tg+50)° C.,more preferably between Tg and (Tg+30)° C. At a temperature lower thanTg, the films are difficult to stretch; but at a temperature higher than(Tg+50)° C., the films could not be uniformly stretched and aretherefore unfavorable. For improving the heat resistance and thedimensional stability thereof, the stretched films are heat-set undertension at a temperature not lower than (Tg+10)° C. but lower than themelting point thereof. Varying the condition for stretching andheat-setting in this stage, the degree of crystallinity of the processedfilms may be controlled.

[0048] Stretched and heat-set under the condition mentioned above, thefilms are oriented to have a degree of crystallinity of from 10 to 60%.Preferably, the degree of crystallinity of the oriented films is from 20to 50%. For example, 20 parts by weight of a compound of formula (1)where R₁ to R₄ are all alkyl groups having one carbon atom and n is 1 isadded to 100 parts by weight of a lactic acid-based polymer, theresulting mixture is sheeted through a T-die into a film, and the filmis then stretched at 50° C. by 2.5 times in the MD direction and by 2.5times in the TD direction (this stretching mode is hereinafterabbreviatedas 2.5×2.5). Next, this is heat-set at 140° C. under tension,and it gives an oriented film having a degree of crystallinity of about30%.

[0049] The aliphatic polyester film of the invention may be produced inany form of rolls, tapes, cut sheets or (seamless) cylinders by suitablydetermining the process condition in accordance with the intendedobject.

[0050] The aliphatic polyester film of the invention is favorable toshopping bags, garbage bags, compost bags, films for packaging foods andconfectionery, films for wrapping foods, films for wrapping cosmeticsand perfumes, films for wrapping medicines, films for wrapping herbs,films for wrapping surgical poultices for stiff shoulders, sprain, etc.,films for agricultural and horticultural use, films for wrappingagricultural chemicals, films for greenhouses, fertilizer bags, filmsfor packaging video or audio magnetic tape cassette products, films forpackaging flexible discs, films for plate making, adhesive tapes,waterproof sheets, sandbags, etc. Of those applications, the film of theinvention is more favorable for packaging, and it forms packages. Theobjects to be packaged with the film are foods such as vegetables,fruits, confectionery; cosmetics, medicines, agricultural chemicals,fertilizer, soil, domestic garbage, compost; electric and electronicproducts such as videos, CDs, MOs, MDs, DVDs, etc. The thickness of thepolyester film of the invention may vary in accordance with the usethereof, and it is generally from 5 to 1000 μm.

[0051] The aliphatic polyester film of the invention maybe formed intobags in various methods of heat sealing, high frequency sealing, fusingor the like. For example, a film produced in the form of cut sheets isfolded in two, and the two sides running from the folded edge areheat-sealed with a heat-sealing bar at a temperature not lower than Tg(glass transition temperature) of the film to form a bag. A rolled film,while unrolled, is folded in two in the TD direction, and it is fused atregular intervals in the MD direction with a fusing bar at a temperaturenot lower than the melting point of the film to form bags. A cylindricalrolled film, while unrolled, is heat-sealed at predetermined regularintervals in the MD direction with a heat-sealing bar at a temperaturenot lower than Tg, and the part just adjacent to the heat-sealed part iscut at predetermined regular intervals in the MD direction to form bags.

[0052] If desired, the aliphatic polyester film of the invention may becoated with a layer having a function of antistatic property, foggingresistance, stickiness, gas barrier capability, airtight adhesiveness,easy adhesiveness or the like. For example, an aqueous coating liquidthat contains an antistatic agent may be applied to one or both surfacesof the film and dried to form an antistatic layer thereon. For applyingsuch an aqueous coating liquid, employable is any known method.Concretely, employable for it is any of doctor-blade coating, spraying,air-knife coating, reverse coating, kiss coating, gravure coating,Meyer's bar coating, roll brushing or the like.

[0053] An acrylic resin adhesive, for example, a copolymer preparedthrough copolymerization of an essential ingredient such as ethylacrylate, butyl acrylate or 2-ethylhexyl acrylate with any other vinylicmonomer is uniformly dissolved in an organic solvent to prepare asolvent-based coating liquid, or it is granularly dispersed in water toprepare an aqueous emulsion-based coating liquid. Thus prepared, thecoating liquid is applied to the film and dried thereon in a knownmethod to thereby make the film adhesive.

[0054] Also if desired, the aliphatic polyester film of the inventionmay be laminated with any other resin or film so as to be coated withthe layer thereof having a function of static charge prevention, foggingresistance, stickiness, gas barrier capability, airtight adhesiveness,easy adhesiveness or the like. For this, employable is any known methodof extrusion lamination, dry lamination or the like.

[0055] The storage modulus (E′) at 20° C. of the aliphatic polyesterfilm of the invention is from 1×10⁷ to 2×10⁹ Pa, and the film is highlyflexible. In addition, the loss tangent (tan δ) at 20° C. of the film isfrom 0.1 to 1.0; and the adhesion power of the film, measured accordingto the method described in the section of Examples mentioned below, isat least 200 g/cm². This means that the film has good self-adhesivenessand adhesiveness to objects to be wrapped with it. Further, the haze ofthe film is from 0.05 to 3%; the heat-resistant temperature thereof isfrom 100 to 170° C.; and the degree of crystallinity thereof is from 10to 60%. The characteristics of the uniaxially oriented aliphaticpolyester film that is produced by at least uniaxially stretching thealiphatic polyester film of the invention are almost the same as above.

EXAMPLES

[0056] The invention is described in more detail with reference to thefollowing Examples. The degree of crystallinity, the storage modulus,tan δ, the haze, the heat resistant temperature, the adhesiveness andthe degree of migration referred to in the Examples are measuredaccording to the methods mentioned below.

[0057] (1) Degree of Crystallinity (%)

[0058] Using a differential scanning calorimeter (Rigaku's ModelTAS100), a melting curve of a sample is drawn. From the peak area of themelting curve, the heat of fusion (ΔH) of the sample is obtained. Basedon the heat of fusion (ΔH₀) of complete crystal, the degree ofcrystallinity (Xc) of the sample is calculated according to thefollowing numerical equation. The standard substance used is indium.

Xc=ΔH/ΔH₀

[0059] (2) Storage Modulus E′ (P_(a)), tan δ:

[0060] Using a dynamic solid viscoelastometer (Rheometric's ModelRSAII), a film sample having a length of 40 mm (MD direction), a widthof 5 mm (TD direction) and a mean thickness of from 5 to 15 μm ismeasured at a temperature falling between −100 and 230° C., at a heatingrate of 5° C./min and at a frequency of 1 Hz. The storage modulus (E′)at 20° C. of the sample is read, and the value tan δ that indicates theratio of the loss Young's modulus (E″) to the storage modulus (E′),(E″/E′) is calculated.

[0061] (3) Haze (%):

[0062] Using a haze meter (by Tokyo Denshoku), the haze value (%) of afilm sample is obtained, and this is converted into a value of thecorresponding film sample having a thickness of 10 μm.

[0063] (4) Heat-Resistant Temperature (° C.)

[0064] A film sample of 14 cm (MD)×3-cm (TD) is attached to a sheet offlat-grain paper having the same width as that of the film, and theflat-grain paper and the film are stuck and fixed to each other at thetwo edges of 2.5 cm length in the MD direction. This is a sample to betested herein. Of the two edges of 2.5 cm length each, the upper edge ofthe film sample thus reinforced with the flat-grain paper is fixed to atool to the full width thereof, and a weight of 10 g is fitted to thecenter of the lower edge of the film sample. In that condition, the filmsample is rapidly put into an air oven that has been conditioned at apredetermined temperature, and heated therein for 1 hour. The sample ischecked as to whether or not it is cut. The test temperature is elevatedat regular intervals of 5° C. After one hour, when the sample is notcut, the temperature is further elevated by 5° C. and the same operationas previously is repeated. The maximum temperature at which the sampleis not cut is read, and this is the heat-resistant temperature of thesample tested.

[0065] (5) Adhesion Power:

[0066] A film sample of 10 cm (MD)×5 cm (TD) is put on a glass sheet(surface roughness Ra=0.7 to 1.5 nm; 150 mm×150 mm×3.0 mm thickness) sothat the contact area may be 50 mm×50 mm. An aluminium plate of 50 mm×50mm×1 mm thickness is put over the film, and a weight is further putthereon so that the load to the film may be 4 KPa. After 10 seconds, thealuminium plate and the weight are removed. The MD edges of the film areheld by the clips fitted to the tips of a push-pull gauge (AikoEngineering's Push-Pull Gauge 9505A). In that condition, the film ispulled at a rate of 200 mm/min by operating the push-pull gauge, and theadhesion power (shear peeling power) of the film is measured. One sampleis measured 5 times, and the maximum and minimum data are cut. Theremaining three data are averaged, and the resulting average indicatesthe adhesion power of the sample.

[0067] (6) Migration:

[0068] A film sample of 10 cm (MD)×10 cm (TD) is left in an atmosphereat 60° C. and 50% RH, and visually checked for the presence or absenceof the plasticizer that has migrated out on the film surface. Based onthe time (days) taken before migration of the plasticizer, the sample isevaluated as follows. ⊚: 60 days or more, ◯: 30 days or more but lessthan 60 days, Δ: 14 days or more but less than 30 days, x: less than 14days.

PRODUCTION EXAMPLE 1

[0069] <Production of Aliphatic Polyester Resin>

[0070] In a 100-liter reactor equipped with a Dien-Stark trap, 10 kg of90 mol % L-lactic acid (impurity content, 0.5 mol %) was heated at 150°C. under 7000 Pa for 3 hours with stirring while water was evaporatedaway, and then 6.2 g of tin powder was added thereto and further stirredat 150° C. and under 4000 Pa for 2 hours for oligomerization. To theoligomer, added were 28.8 g of tin powder and 21.1 kg of diphenyl etherand reacted at 150° C. and under 4700 Pa for azeotropic dehydration. Theevaporated water and solvent were separated in a water separator, andthe aqueous layer was successively drawn out and the solvent only wasreturned to the reactor. After 2 hours (in this stage, the impuritycontent was 0.05 mol %), the organic solvent to be returned to thereactor was passed through a column filled with 4.6 kg of MolecularSieve 3A before being returned to the reactor. In that condition, thereaction was effected at 150° C. and under 4700 Pa to obtain a solutionof polylactic acid having a polystyrene-based weight-average molecularweight of 120,000. The solution was diluted with 44 kg of dewatereddiphenyl ether added thereto, and then cooled to 40° C., and thedeposited crystal was taken out through filtration. This was washedthree times with 10 kg of n-hexane, and then dried at 60° C. and under7000 Pa. The resulting powder was stirred along with 12 kg of 0.5 Nhydrochloric acid and 12 kg of ethanol added thereto, at 35° C. for 1hour, and then taken out through filtration. Dried at 60° C. and under7000 Pa, 6.1 kg (yield, 85% by weight) of polylactic acid powder havinga mean particle size of 30 μm was obtained. The polystyrene-basedweight-average molecular weight of the polymer was about 120,000.

PRODUCTION EXAMPLE 2

[0071] <Production of Compound Al (Tetraacetyldiglycerin)>

[0072] 84 g of diglycerin and 415 g of acetic anhydride were put into areaction flask, to which was added 2.5 g of strong acid ion-exchangeresin (Dow Chemical's trade name, Dowex MSC-1). With stirring, this wasreacted at 80 to 90° C. for 1 hour. After cooled, the ion-exchange resinwas removed through filtration, and the formed acetic acid and thenon-reacted acetic anhydride were evaporated away under reducedpressure. This gave 161.5 g of tetraacetyldiglycerin (hereinafterreferred to as Compound Al). Compound Al is represented by formula (1)where R₁ to R₄ are all alkyl groups having one carbon atom and n is 1.Its acid value is 0.2, and its hydroxyl value is 3.1.

PRODUCTION EXAMPLE 3

[0073] <Production of Compound A2 (Tetraoctanoyldiglycerin)>

[0074] 500 g of chloroform, 42 g of diglycerin and 195 g of octanoicacid chloride were put into a reaction flask, to which was dropwiseadded 95 g of pyridine at 20 to 30° C. Next, this was stirred at 40° C.for 2 hours to react the compounds. After the reaction, the reactionliquid was washed with water, chloroform was evaporated away, and 160 gof tetraoctanoyldiglycerin (hereinafter referred to as Compound A2) wasobtained. Compound A2 is represented by formula (1) where R₁ to R₄ areall alkyl groups having 7 carbon atoms and n is 1. Its acid value is0.5, and its hydroxyl value is 4.5.

PRODUCTION EXAMPLE 4

[0075] <Production of Compound A3 (Pentastearoyltriglycerin)>

[0076] 500 g of chloroform, 24 g of triglycerin and 167 g of stearicacid chloride were put into a reaction flask, to which was dropwiseadded 43 g of pyridine at 20 to 30° C. Next, this was stirred at 40° C.for 2 hours to react the compounds. Then, this was processed in the samemanner as in Production Example 3, and 142 g of pentastearoyltriglycerin(hereinafter referred to as Compound A3) was obtained. Compound A3 isrepresented by formula (1) where R₁ to R₄ are all alkyl groups having 17carbon atoms and n is 2. Its acid value is 0.4, and its hydroxyl valueis 2.9.

PRODUCTION EXAMPLE 5

[0077] <Production of Compound A4 (Dodecabehenoyldecaglycerin)>

[0078] 500 g of chloroform, 19 g of decaglycerin and 108 g of behenicacid chloride were put into a reaction flask, to which was dropwiseadded 26 g of pyridine at 20 to 30° C. Next, this was stirred at 40° C.for 2 hours to react the compounds. Then, this was processed in the samemanner as in Production Example 3, and 110 g ofdodecabehenoyldecaglycerin (hereinafter referred to as Compound A4) wasobtained. Compound A4 is represented by formula (1) where R₁ to R₄ areall alkyl groups having 21 carbon atoms and n is 9. Its acid value is0.3, and its hydroxyl value is 2.1.

EXAMPLE 1

[0079] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1, 30parts by weight of Compound Al and 5 parts by weight of decaglycerinoleate (Riken Vitamin's trade name, Poem J-0381—this is hereinafterreferred to as Compound B1) were melt-kneaded and extruded out at 180°C. to give a non-oriented film having a thickness of 80 μm. Thenon-oriented film was stretched by 2.5 times in the MD direction andthen by 3 times in the TD direction, and thereafter this was heat-set at130° C. Then, this was cooled with air at 30° C. to obtain an orientedfilm having a mean thickness of 10 μm. The degree of crystallinity ofthe thus-obtained film was 15%. The test data of the elastic modulus,tan δ, haze, heat-resistant temperature, adhesion power and migrationresistance of the film are given in [Table 1].

EXAMPLE 2

[0080] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 25parts by weight of Compound Al were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 60 μm. Thenon-oriented film was stretched by 2 times in the MD direction and thenby 2.5 times in the TD direction, and thereafter this was heat-set at130° C. Then, this was cooled with air at 30° C. to obtain an orientedfilm having a mean thickness of 10 μm. The degree of crystallinity ofthe thus-obtained film was 25%. The test data of the elastic modulus,tan δ, haze, heat-resistant temperature, adhesion power and migrationresistance of the film are given in [Table 1].

EXAMPLE 3

[0081] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 55parts by weight of Compound A2 were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 50 μm. Thenon-oriented film was stretched by 1.5 times in the MD direction andthen by 2.5 times in the TD direction, and thereafter this was heat-setat 130° C. Then, this was cooled with air at 30° C. to obtain anoriented film having a mean thickness of 10 μm. The degree ofcrystallinity of the thus-obtained film was 12%. The test data of theelastic modulus, tan δ, haze, heat-resistant temperature, adhesion powerand migration resistance of the film are given in [Table 1].

EXAMPLE 4

[0082] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 30parts by weight of Compound A3 were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 40 μm. A filmof the polymer obtained in Production Example 1, having a thickness of10 μm, was laminated on both surfaces of the non-oriented film, and thenthis was stretched by 2.5 times in the MD direction and then by 3 timesin the TD direction, and thereafter heat-set at 130° C. Then, this wascooled with air at 30° C. to obtain an oriented film having a meanthickness of 10 μm. The test data of the elastic modulus, tan δ, haze,heat-resistant temperature, adhesion power and migration resistance ofthe film are given in [Table 1].

EXAMPLE 5

[0083] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 40parts by weight of Compound A3 were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 60 μm. A filmof polybutylene succinate having a thickness of 10 μm was laminated onboth surfaces of the non-oriented film, and then the non-oriented filmwas stretched by 2.5 times in the MD direction and then by 3 times inthe TD direction, and thereafter heat-set at 130° C. Then, this wascooled with air at 30° C. to obtain an oriented film having a meanthickness of 10 μm. The test data of the elastic modulus, tan δ, haze,heat-resistant temperature, adhesion power and migration resistance ofthe film are given in [Table 1].

EXAMPLE 6

[0084] Using a 40-mm inflation molding machine (die diameter, 40 mm),pellets containing 100 parts by weight of the polymer obtained inProduction Example 1 and 20 parts by weight of Compound Al were moldedinto an inflation film having a flat width of 150 mm and a thickness of12 μm. Thus obtained, the film was heat-set at 140° C., and then cooledwith air at 30° C. The degree of crystallinity of the thus-obtained filmwas 18%. The test data of the elastic modulus, tan δ, haze,heat-resistant temperature, adhesion power and migration resistance ofthe film are given in [Table 1].

COMPARATIVE EXAMPLE 1

[0085] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 5parts by weight of Compound Al were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 80 μm. Thenon-oriented film was stretched by 2.5 times in the MD direction andthen by 3.0 times in the TD direction, and thereafter this was heat-setat 130° C. Then, this was cooled with air at 30° C. to obtain anoriented film having a mean thickness of 10 μm. The degree ofcrystallinity of the thus-obtained film was 30%. The test data of thefilm are given in [Table 2].

Comparative Example 2

[0086] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 70parts by weight of Compound Al were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 70 μm. Thenon-oriented film was stretched by 2 times in the MD direction and thenby 3 times in the TD direction, and thereafter this was heat-set at 130°C. Then, this was cooled with air at 30° C. to obtain an oriented filmhaving a mean thickness of 10 μm. The degree of crystallinity of thethus-obtained film was 15%. The test data of the film are given in[Table 2].

COMPARATIVE EXAMPLE 3

[0087] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 25parts by weight of Compound A4 were melt-kneaded and extruded out at180° C. to give a non-oriented film having a thickness of 60 μm. Thenon-oriented film was stretched by 2 times in the MD direction and thenby 2.5 times in the TD direction, and thereafter this was heat-set at130° C. Then, this was cooled with air at 30° C. to obtain an orientedfilm having a mean thickness of 10 μm. The degree of crystallinity ofthe thus-obtained film was 20%. The test data of the film are given in[Table 2].

COMPARATIVE EXAMPLE 4

[0088] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example 1 and 15parts by weight of decaglycerin laurate (Riken Vitamin's trade name,Poem J-0021—this is hereinafter referred to as Compound B2) weremelt-kneaded and extruded out at 180° C. to give anon-oriented filmhaving a thickness of 60 μm. The non-oriented film was stretched by 2times in the MD direction and then by 3 times in the TD direction, andthereafter this was heat-set at 130° C. Then, this was cooled with airat 30° C. to obtain an oriented film having a mean thickness of 10 μm.The degree of crystallinity of the thus-obtained film was 15%. The testdata of the film are given in [Table 2].

COMPARATIVE EXAMPLE 5

[0089] Using an extruder equipped with a T-die, pellets containing 100parts by weight of the polymer obtained in Production Example land 50parts by weight of tetraglycerin oleate (Riken Vitamin's trade name,Poem J-4581—this is hereinafter referred to as Compound B3) weremelt-kneaded and extruded out at 180° C. to give a non-oriented filmhaving a thickness of 80 m. The non-oriented film was stretched by 2.5times in the MD direction and then by 3 times in the TD direction, andthereafter this was heat-set at 130° C. Then, this was cooled with airat 30° C. to obtain an oriented film having a mean thickness of 10 μm.The degree of crystallinity of the thus-obtained film was 15%. The testdata of the film are given in [Table 2]. TABLE 1 Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Compound A type A1 A1 A2 A3 A3A1 wt. pts. 30 25 55 30 40 20 Compound B type B1 — — — — — wt. pts. 5 —— — — — Constitution of Film single-layered single-layeredsingle-layered multi-layered multi-layered single-layered Draw Ratio(times) 2.5 × 3.0 2.0 × 2.5 1.5 × 2.5 2.5 × 3.0 2.5 × 3.0 1.3 × 3.0Degree of 15 25 12 — — 18 Crystallinity (%) Elastic Modulus (Pa)   1 ×10⁹   6 × 10⁸   6 × 10⁷   5 × 10⁸   6 × 10⁸  1.2 × 10⁸ tan δ 0.4 0.5 0.60.5 0.4 0.5 Haze (%) 0.8 1 0.6 0.8 2.5 0.9 Adhesion Power 220 250 420280 260 320 (g/cm²) Heat-resistant 135 140 130 135 140 130 Temperature(° C.) Migration Resistance ⊚ ⊚ ⊚ ⊚ ⊚ ⊚

[0090] TABLE 2 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp. Ex. 4 Comp. Ex.5 Compound A type A1 A1 A4 — — wt. pts. 5 70 25 — — Compound B type — —— B2 B3 wt. pts. — — — 15 50 Constitution of Film single-layeredsingle-layered single-layered single-layered single-layered Draw Ratio(times) 2.5 × 3.0 2.0 × 3.0 2.0 × 2.5 2.0 × 3.0 2.5 × 3.0 Degree of 3015 20 15 15 Crystallinity (%) Elastic Modulus (Pa)  2.5 × 10⁹   8 × 10⁶ 2.4 × 10⁹   8 × 10⁸   1 × 10⁸ tan δ 0.2 0.8 0.2 0.4 0.5 Haze (%) 0.80.9 1.1 0.9 0.8 Adhesion Power 100 600 120 150 150 (g/cm²)Heat-resistant 150 110 140 150 135 Temperature (° C.) MigratioResistance ⊚ x ⊚ ◯ x

EXAMPLE 7

[0091] The film obtained in Example 1 was cut into sheets each having alength of 180 mm and a width of 500 mm. Each sheet was folded in two inthe TD direction, and the two sides running from the folded edge wereheat-sealed at 100° C. The bags thus formed had a width at the openingof about 175 mm and a depth of 250 mm. About 500 g of tomatoes were putinto each bag, of which the opening was drawn and fixed with a bondingtape. Tomatoes were thus packaged in each bag.

EXAMPLE 8

[0092] The inflation film obtained in Example 6, which had a flat widthof 150 mm and a thickness of 12 μm, was fused at regular intervals of250 mm in the MD direction, at a fusing temperature of 280° C., and thencut at the fused intervals to give bags each having a width at theopening of 150 mm and a depth of about 245 mm. About 500 g of carrotswere put into each bag, of which the opening was drawn and fixed with abonding tape. Carrots were thus packaged in each bag.

ADVANTAGES OF THE INVENTION

[0093] The aliphatic polyester film obtained from the aliphaticpolyester resin composition of the invention keeps the degradability inthe natural environment that is intrinsic to lactic acid-based polymer,and has good heat resistance, flexibility, transparency andadhesiveness, and, in addition, the plasticizer does not migrate on thesurface of the film. Accordingly, the film is favorably used in a broadrange for various industrial materials, for example, for films forwrapping or packaging foods, electronic appliances, medicines,chemicals, cosmetics, etc., for films for agricultural use, for filmsfor civil engineering and construction use, for adhesive tapes, etc.Even when the film is discarded after used, it does not accumulate asindustrial wastes or domestic wastes.

1. An aliphatic polyester resin composition comprising 100 parts byweight of an aliphatic polyester resin and from 10 to 60 parts by weightof at least one compound of a formula (1):

wherein n indicates an integer of from 1 to 9, R₁ to R₄ eachindependently represent an alkyl group having from 1 to 17 carbon atoms,and when n is 2 or more, R₃ may differ in different units:
 2. Analiphatic polyester film having at least one layer of a film of thealiphatic polyester resin composition according to claim
 1. 3. Thealiphatic polyester film according to claim 2, of which a storagemodulus (E′) at 20° C. is from 1×10⁷ to 2×10⁹ Pa, and a loss tangent(tan δ) indicating the ratio of a loss Young's modulus (E″) to thestorage modulus (E′), (E″/E′) is from 0.1 to 1.0.
 4. The aliphaticpolyester film according to claim 2 or 3, wherein the aliphaticpolyester is at least one polyester selected from polylactic acid, and acopolymer of lactic acid with any other aliphatic hydroxycarboxylicacid.
 5. The aliphatic polyester film according to any one of claims 2to 4, of which the haze is from 0.05 to 3% when its thickness is 10 μm.6. The aliphatic polyester film according to any one of claims 2 to 4,of which the heat-resistant temperature falls between 100 and 170° C. 7.The aliphatic polyester film according to any one of claims 2 to 4, ofwhich the degree of crystallinity is from 10 to 60%.
 8. The aliphaticpolyester film according to any one of claims 2 to 4, of which thethickness is from 5 to 1000 μm.
 9. The aliphatic polyester filmaccording to any one of claims 2 to 4, which is for wrapping orpackaging.
 10. A package of an object wrapped or packaged with thealiphatic polyester film according to any one of claims 2 to 4.